You might also add non-chord tones to your melody. They add interest and some tension, making it more interesting. A melody consisting only of chord tones might be really boring, especially at slow harmonic rhythm. I guess you are familiar with the non-chord tones? If you aren't, then check
this.
It is important to be aware of the contour of your melody... It usually has one highest point (climax) and one lowest. It's direction might be from downwards to upwards or vice versa. Of course, it depends on what you want to convey with your melody. It might also be a more neutral one, evolving closely around certain pitch, without clearly presented climax.